Drawing reproduction



Sept 10, 1946. \R. J. wlRsHlNG ET AL 2,407,596

DRAWING REPRODUCTION Filed Dec. 24, 1943 Patented Sept. 10, 1946 i UNITED STATES PATENT OFFICE DRAWING REPRODUCTION Ralph J. Wirshing and Frank E. Smith, Detroit, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Claims.

This invention relates to means for reproducing drawings of considerable size. As is well-known in the arts, where large structures are fabricated, such as in automobile and aircraft work, it is often necessary to provide full size drawings of parts or assemblies, These drawings represent considerable work in their origin, and because of their size it is necessary to make the originals on some substantial backing so that they will not be injured by ordinary use, and also so that their dimensions will remain in proper tolerance. These drawings have been applied to large sheet material, and in some instances steel sheets of relatively thin dimensions, and in order to produce prints or reproductions therefrom, various methods have been used, some involving the use of X rays and others luminescent material activated by ordinary light.

One method which has been used is to apply to a large steel, or otherwise opaquebacking sheet, a layer of material acting as a vehicle for excitable fluorescent material and then marking on thisv layer with opaque lines to produce the drawing; next exciting this fluorescent layer and causing the sensitized sheet in contact therewith to be subjected to such excitation and thus reproduce the drawing. This excitation may be od has been to use a similar excitable undercoat and entirely cover the surface oi' the saine with an opaque layer of lacquer base, then scribing the drawing in the upper layer to expose lines of the excitable or iiuorescent surface and to obtain prints therefrom in thel same manner.

However, when using drawings including X ray excitable means and exposing the same to X rays during printing, certain fogging effects have appeared in the areas which do not form line surfaces, in other words, the substantially unexposed areas. This of course detracts from the contrast of the lines and the unexposed surfaces. Furthermore, the scribing surface has been composed of material which does not cut as clearly and as easily as desired.

It is therefore an object of the present invention to provide an over-coat surface for luminescent layers which acts as a screen to the passage of undesired X-radiation.

It is a further object of our invention to provide means acting as an over-coat which may be easily and smoothly scribed.

It is a still further object of our invention to provide over-coating means providing the necessary color contrast so that the drawing cut therein may be. easily discerned.

' either by X ray or visible light. Another meth- With these and other objects in view, the embodiments of our invention may be best understood by reference to the following specification and claims and the illustration in the accompanying drawing in which the figure illustrates a composite section of a master base from which reproductions can be made. In this instance the master drawing is made on a steel backing sheet of suitable dimensions with the drawing to be reproduced. This cleaned sheet is first treated with a coat of oil type primer so that "the next additional surface |may adhere hereto properly. There is next applied a surface embodying a fluorescent Y or phosphorescent excitable layer which may be barium chlorofluoride ineither a lacquer or synthetic enamel vehicle. Over this layer may be applied a layer of clear lacquer which is optional, and if enamel is used as a base of the phosphorescent layer, this is not necessary.

Over this last clear layer is applied a layer of* opaque lacquer which` is the layer in which the drawing is scribed. This layer is composed of colored pigment nitrocellulose lacquer containing some lead 'chromate and beeswax mixed therein and a small quantity of magnesium siii-- cate. The use of lead chromate pigment is to act as a screen against the passage of X rays and cut down the-.fogging in the unexposed areas. Beeswax is introduced in order to make the surface more easily cut into and provide smooth cutting and no tearing of edgesofthe coating.- The magnesium silicate produces a non-glare or atness of the surface. In this coating or layer the color pigment may be any Vshade desired,

and if only one over-coat layer were used, the lines drawn therein would be visible because of the contrast between this color and the exposed luminescent layer. This does not result in distinct easily read lines or drawings. `In order to provide clearly legible lines, the color pigment used in the first coating may be relatively dark, such as dark blue or dark green, and there is applied as a second layer one similar to that just described, the only differences being that it is thinner and the color pigment in the top layer is of light contrasting color to that in the one under it.

As an example of colors which have been satisfactory, both a light blue top coat on a dark blue and light green on dark green give an excellent contrast. When the drawing is therefore cut with the scribing tool, the two top layers are cut through to expose the clear lacquer or upper surface of the enamel in the fluorescent layer and in so doing shows the contrast between the light and dark top layers. This provides a draw.

or dried thoroughly before the application of the g next, and in some instances, as for example in the X ray sensitive layer; the surface may be sanded lightly before the next layer is applied. The

layer of clear lacquer may be appliedas a sheetv and laminated to the upper surface of the luminescent layer, and if a sheet is used, all ofthe-` layers may be applied to opposite sides of the clear lacquer sheet, except the steel backing of course, and the same may be made up exibly as an assembly and only applied to the steel backing sheet `prior to the application of the drawing to the upper surface.

From the foregoing it will be evident thatWe hav-e improved the scribing surface by the addition of X-ray screening means, made the same softer for scribing purposes, and provided a satisfactory, easily discernible contrast so the drawing may be read.

rWe claim:

1. In a master drawing, a supporting sheet, a

layer of luminescentmaterial on one face of the sheet capable of being excited by X-radiation, a coating over theluminescent layer including beeswax and a color pigment so that this coating may be readily scribed to provide the drawing and expose the luminescent lines for printing reproductions. 2. In a master drawing having a layer of excitable luminescent material, a coating therefor in which the drawing may be scribed comprising, a lacquer base and means therein to absorb radiation'for exciting the luminescent material whereby proper contrast may be obtained between the scribed and unscribed areas.

-3. In a master drawing having a layer of excitable luminescent material, a coating therefor in which the drawing may be scribed comg prising, a lacquer basefmeans therein to absorb radiation for exciting the luminescent material and means to soften'the -coating when dry so that the same may be readily scribed and will provide proper contrast between the scribed and l unscribed areas.

4. Ina master drawing having a layer of excitable luminescent material, a coating therefor in which the drawing may be scribed comprising, a lacquer base, X-radiation absorbing means in said lacquer and beeswax in said lacquer so that the resultant coating may be easily scribed due to the presence of the beeswax and the absorbing means will reduce fogging,

5. In a master drawing having a layer of excitable luminescent material, a coating therefor in which the drawing may be scribed comprising, a lacquer base, color pigment in the lacquer and lead chromate mixed therein so that the resultant coating may `be scribed and the lead will absorb `X--radiation to reduce fogging.

' 6. Ina master drawing having a layer of excitable luminescent material, a coating therefor in which the drawing may be scribed comprising, a lacquer base, color pigment therein, and a substantial amount of beeswax mixed therein so that the coating when dry maybe easily `scribed and provide color contrast.

7. In a master drawing having alayer of excitable luminescent material, a coating therefor in i whichthe drawing may be scribed comprising, a lacquer base, color pigment therein, lead chromate mixed therewith and beeswax,V all thoroughly mixed together and applied as a coating so that the drawing may be scribed therein.

S'. In a master drawing having a layer of excitable luminescent material, a plurality of scribable coatings ofA different shades of color successively applied to the luminescent layer so that as the drawing is scribed therein, the contrast in shade will make the marks readily discernible.

9. In a masterl drawing havinga layer of excitable luminescent material, a rst coating containing a color pigment applied over the layer,-a second coating containing a pigment of different shade or, color applied over the-first so Athat when the 1drawing is scribed through the coatings, a contrast makes the lines readily discernible.

lil. In a master drawing having a` layer of excitable luminescent material, a first coating there-fer including binder, color pigment, softening agent and absorbing means for the excitation rays, and a second coatingoverthe first includingfbinder, softening agent and adiiferent color pigment for contrast.

RALPH J. WIRSHING.

FRANK E. SMITH. 

